Production of permanganates.



Patented May 12, 1903.

Fries.

ATENT WILHELM HICKMANN, OF FRANKFORT-ON-THE-MAIN, GERMAN Y, ASSIGNOR TO SOCIETY OHEMISOHE FABRIK GRIESHEIM ELECTRON, OF FRANKFORT- ON-THE-MAIN, GERMANY.

PRODUCTION OF PERMANGANATES.

SPECIFICATION forming part of Letters Patent No. 727,792, dated May 12, 1903.

Application filed March 3, 1903. Serial No. 145,991. (No specimens.)

T at whom zit may concern.-

Be it known that I, WILHELM HICKMANN, a subject of the German Emperor, residing and having my post-office address at 3 Neue 5 Krame, Frankfort-on-the-Main, Germany,

have invented certain new and useful Improvements in the Production of Permanganates, of which the following is a specification.

Among permangauates those which are almost exclusively used in practice are the potassium and the sodium permanganates. These are prepared in a simple manner from the manganates obtained by fusing processes.

I 5 The permanganates of other metals cannot generally be produced in this manner,because the corresponding manganates cannot be obtained by a similar fusing process, except in a form which renders them little adapted for further treatment. Although the production of such permanganates by the metathesis of suitable salts and alkali permanganates is possible in some cases, the process is not, however, susceptible of general application.

It is not possible, for instance, to obtain calcium permanganate by the metathesis of calcium chlorid and potassium permanganate, which is easily obtainable pure in large quantities. It has been found that these reactions,

which cannot be obtained in a purely-chemical manner, take place when mixtures of solutions of alkali permanganates or manganates are, together with the oxygenated or halogen compounds of metals of the aforesaid 5 class, subjected in a suitable manner to the action of the electric current.

The following examples will explain how the process is carried out in practice when applied to the preparation of calcium per- 0 manganate from potassium permanganate.

Exam pleI: An electrolytic cell is employed the anode-compartment of which is separated from the cathode compartment by a diaphragm or other suitable means, so that the 5 anode liquid is prevented from mixing with the cathode liquid and a reduction of per manganate is avoided. Both compartments are closed at the top and provided withoutlet-pipes through which the gases escape separately. The cathode-compartment is filled with diluted potash lye and the anode-compartment with a saturated solution of potassium permanganate, which is maintained in the state of saturation by means of sieves suspended in the-said liquid and filled with potassium permanganate. Washed calcium hydroxid is introduced into the anode-compartm ent, this being preferably done gradually as the operation is proceeding, so as to prevent the diaphragm being stopped. If be now an electric current is passed through the electrolytic cell, the potassium ions migrate into the anode-compartment and form there potash lye, while at the same time hydrogen is evolved. The M110 ions remain in the anode-compartment, and from these oxygen is evolved, while at the same time permanganic acid is formed, which as soon as itforms combines with the calcium hydroxid held in suspension, and thus forming calcium permanganate. Then the calcium salt formed in the anode liquid has reached a certain amount, it is advisable to interrupt the electrolysis and to separate by crystallization the potassium permanganate that is still remaining in the anode liquid, this presenting no difliculty.

Example II: The electrolytic cell is arranged as described in Example I. The cathode-compartment contains a saturated solution of potassium chlorid. The anode-compartment is filled with a saturated solution of about one hundred kilograms of potassium permanganate,to which are added twenty kilograms of calcium chlorid, (021131 Sieves suspended in the solution and filled with KMnO as in the previous example, maintain the solution constantly saturated with KMnO and prevent it getting poor in potassium ions. It now a current of, say, two to 0 three amperes per square decimeter of electrode is passed through the cell, 01 ions are discharged at the anode and escape in form of chlorin gas. Of the positive ions the potassium ions, which are most readily set 5 in motion and are present in a high degree of concentration, effect the conduction of the current from the anode to the cathode and migrate into the cathode-compartment, forming therein potash lye, While hydrogen 10o is set free. The calcium ions of the CaOl ions, which probably predominate on account of thegradual dissociation of the calciumchlorid, remain behind or migrate in but very small numbers on account of their low degree of concentration and the frictional resistance opposing their motion, which resistance is further greatly increased by the diaphragm. A migration of the Ca ions into the cathodecompartment would decrease the yield of calcium permanganate; butas this migration is very small in comparison to that of the potassium ions it cannot aifect the process in any marked degree. The action in the anodecompartment is as follows: The Cl ions escape therefrom in the form of gaseous chlorin. At the same time the potassium ions migrate toward the cathode-compartment. The corresponding quantities of Ca (or CaOl) and MnO ions remain in the anode-compartment and combine together to form calcium permanganate. The influence of the OH ions, which migrate in smaller number into the anode-compartment and might give rise to an intermediate formation of hypochlorous acid or chloric acid, need not be taken into account, as thesesubstances are not verystable under these circumstances. The electrolysis might be continued until the cathode-space contains a quantity of potash lye corresponding to the amount of calcium chlorid used; but it is preferred to stop the operation before this stage is reached. The yield in calcium permanganate corresponds to the amount of potash lye obtained in the cathode-compartment.

The solution in the anode-compartment contains at the end of the operation a mixture of potassium permanganate, calcium permanganate, and possibly some calcium chlorid. The calcium permanganate is obtained in a state of purity by the usual process of fractional crystallization. The mother-lyes are used again in the process. The purification of the potash l-ye and the collecting and utilization of the gases evolved in the operation are effected by Well-known methods.

Having now particularly described and ascertained the nature of the said invention and in what manner the same is to be performed, I declare that what I claim is- A process for the electrolytic preparation of the permanganates of alkaline-earth metals, and other heavy metals, with simultaneous production of alkaline lye, hydrogen, and oxygen, or chlorin, which process consistsin subjecting a mixture consisting of a solution of an alkali permanganate or alkaline manganate and an oxygenated or halogen compound of one of the metals Whose permanganate salt is to be obtained, to the action of an electric current, the electrodes being separated by means of a diaphragm or other suitable device, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

WILHELM HICKMANN.

Witnesses:

FRANZ HASSLACHER, MICHAEL VoLKE. 

